# How to plot the Coulomb stress change on nodal planes in GMT6.5 (Windows)?

I am using GMT6.5 (windows). I have calculated coulomb stress change on nodel planes. But I don’t know how to plot the output in GMT.
The output file looks like this:
|year|month|day|hour|minute|lon.|lat.|depth|magnitude|strike1|dip1|rake1|shear1|normal1|coulomb1|strike2|dip2|rake2|shear2|normal2|coulomb2|
|2022|9|17|13|41|121.160797|23.084|8.61|6.6|201.449997|61.540001|15.04|1.461529|-0.453529|1.280118|104.150002|76.809998|150.699997|1.46163|0.68777|1.736738|

As far as I can tell, your output is a single point (point source approximation?). There’s nothing to be plotted here other than a single point with two Coloumb estimates each per nodal plane.

The coulomb stress change is calculated on nodal planes. For the learning purpose I only shown one point. However the output looks like this:

year month day hour minute lon. lat. depth magnitude strike1 dip1 rake1 shear1 normal1 coulomb1 strike2 dip2 rake2 shear2 normal2 coulomb2
- - - - - (deg) (deg) (km) - (deg) (deg) (deg) (bar) (bar) (bar) (deg) (deg) (deg) (bar) (bar) (bar)
2022 9 17 13 41 121.160797 23.084 8.61 6.6 201.449997 61.540001 15.04 1.461529 -0.453529 1.280118 104.150002 76.809998 150.699997 1.46163 0.68777 1.736738
2022 9 17 14 35 121.178001 23.0993 9.33 5.33 233.419998 35.939999 88.510002 0.306129 -0.698723 0.02664 55.25 54.080002 91.080002 0.306196 -1.106357 -0.136347
2022 9 17 14 45 121.193703 23.116699 5.84 5.84 194.039993 63.25 23.610001 0.091454 -2.364743 -0.854443 92.910004 69.040001 151.190002 0.091477 -0.843406 -0.245885
2022 9 17 16 44 121.182999 23.1012 8.8 4.57 80.989998 41.509998 83.900002 -0.368312 -0.448963 -0.547898 269.109985 48.779999 95.370003 -0.368292 -0.120805 -0.416615
2022 9 17 18 3 121.311798 23.0993 15.51 4.92 219.240005 37.450001 109.730003 -0.653374 1.499737 -0.053479 14.93 55.080002 75.5 -0.653351 0.122689 -0.604275
2022 9 17 19 2 121.207497 23.0165 9.86 3.87 10.5 27.35 118.940002 -0.997402 0.061166 -0.972935 158.589996 66.290001 75.949997 -0.997526 -0.015321 -1.003655
2022 9 17 20 28 121.314796 23.102301 13.55 3.74 347.809998 51.459999 29.67 0.641695 0.427562 0.81272 238.270004 67.220001 137.479996 0.641436 3.355614 1.983681
2022 9 17 21 11 121.339699 23.1003 17.24 4.03 227.300003 37.380001 112.449997 -0.922702 1.904062 -0.161077 19.83 55.869999 73.730003 -0.922841 0.16517 -0.856773
2022 9 17 21 41 121.330704 23.1103 15.88 4.25 217.860001 33.880001 110.169998 -0.893805 1.543683 -0.276332 13.99 58.439999 76.959999 -0.893618 0.28914 -0.777962

There are more rows…

You’ll plot Coulomb stress from one nodal plane at a time, using a grid of lat, lon, Coulomb stress. This is already documented in section 5.9 of the Coulomb manual: https://pubs.usgs.gov/of/2011/1060/of2011-1060.pdf
When you have the xyz grid, you can follow this GMT example to make your figure: https://docs.generic-mapping-tools.org/6.2/gallery/ex02.html

The only step missing here is converting your xyz to grid before using grd2cpt, which you will do by using the xyz2grd GMT function.

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